A number of approaches have been proposed in the manufacture of impellers. In most cases, the manufacture is achieved through the formation of the desired shape(s) from plate substrate, for example formed sheet metal. A primary problem with this prior art approach is that, in many circumstances, it is difficult or impractical to use preferred durable materials, such as certain metals, to achieve the configuration desired. In order to obtain a hydrofoil impeller design, for example, the thickness of the impeller blade must vary along the mean chamber line from the leading edge of the impeller to the trailing edge. The shape and tortuosity can dramatically affect impeller performance, but are difficult to control using standard processing techniques.
Generally, shortcomings of the prior art arise from (1) difficulties in maintaining uniformity in mass production and (2) lack of adequate dimensional accuracy in complex patterns for use in current impeller technology. Additionally, modifying the shape of an impeller blade to achieve better impeller performance has many costs associated with the design, testing, and tooling required to arrive at the desired blade configuration. Thus, there is a need for an improved method for impeller design and manufacture.
With the increased use of Computer Aided Design (CAD) solid modeling systems, a new technique of manufacturing technology has emerged that enables translation of the CAD output data into a three-dimensional (3-D) physical object. This technology is commonly referred to as solid free form fabrication (SFF) or layer manufacturing, which entails building an object on a layer-by-layer and point-by-point basis. CAD with SFF technologies allow for greater repeatability which allows for high quality mass production of the object. Forming objects automatically in three dimensions is useful in verifying a CAD database, evaluating design feasibility, testing part functionality, assessing aesthetics, checking ergonomics of design, aiding in tool and fixture design, creating conceptual models and sales/marketing tools, generating patterns for investment casting, reducing or eliminating engineering changes in production, and providing small production runs.
On the other hand, the resin materials that are currently available for SFF are also subject to certain manufacturing and process limitations in structural stability and rigidity, in chemical resistance and abrasion, and in manufacturing cost.
Accordingly, the need exits for a cost effective solution to increasing impeller performance without the significant investment required for reconfiguring and tooling a new impeller blade. The present invention fulfills these and other needs, and overcomes the drawbacks of the prior art, at least to some extent.